The present disclosure relates to dividers/combiners, and in particular, to such dividers/combiners having an inductively uncoupled section with a bridging assembly across the outputs.
Dividers are circuits that divide a signal into a plurality of signals. An N-way divider divides a signal into N signals. Conversely, a combiner combines a plurality of signals into a single signal. The same circuit can be a divider or combiner, depending on the direction of current flow, i.e., whether the single port is an input port or an output port. As used herein, then, the use of the term “divider” also means “combiner”.
In U.S. Pat. No. 3,091,743, Wilkinson disclosed a power divider in which one end of each of a plurality of branch lines are connected to a common node or port, and the other end of each line is connected to a second node via an interconnecting resistor. In the simple case of two branch lines, the two interconnecting resistors form an isolating interconnecting resistor that connects the two branch ends of the lines. In his article, A Class of Broadband Three-Port TEM-Mode Hybrids, IEEE Transactions on Microwave Theory and Techniques, Vol. MTT-16, No. 2, February 1968, Cohn extended the single section of Wilkinson to multiple cascaded sections formed of pairs of line lengths and interconnecting resistors. The increased number of sections resulted in improved VSWR, isolation, and bandwidth.
Two spaced-apart conductive lines are inductively coupled when they are spaced closely enough together for energy flowing in one to be induced in the other electromagnetically and/or electrostatically. The amount of energy flowing between the lines is related to the dielectric and magnetic media the conductors are in and the spacing between the lines. Even though electromagnetic fields surrounding the lines are theoretically infinite, lines are often referred to as being closely or tightly coupled, loosely coupled, or uncoupled, based on the relative amount of coupling. The amount of coupling may be defined by a coupling coefficient. However, as a practical measure, two lines may be considered to be inductively coupled when a detectable signal is coupled from one line onto the other. A threshold of coupling may be appropriate to distinguish between coupled and uncoupled lines. In most applications, two lines that have less than 20 dB inductive coupling between them are considered to be uncoupled lines. In some applications, lines that have less than 100 dB are considered to be uncoupled lines. In terms of a coupling coefficient, two lines may be considered to be closely coupled if the coupling coefficient is greater than 0.1. Thus, two lines may be considered as loosely coupled or substantially uncoupled if they have a coupling coefficient of less than 0.1.